Abstract

X-ray photoelectron spectroscopy (XPS) has been used to study surfaces, produced by fracture in-vacuo, of praseodymium sodium silicate glasses of nominal composition xPr(2)O(3)0.3Na(2)O.(0.7-x)SiO2 (0.0less than or equal toxless than or equal to0.075). The Pr 3d spectra show intense satellite structure 4.1 eV below the main photoelectron peak with an integrated intensity ratio ( satellite:main) of similar to0.35 in all the glasses. These observations indicate the presence of only trivalent Pr in these glasses. The O 1.s core level spectra show significant composition dependent changes. Two distinct peaks are resolvable arising from the bridging oxygen (BO) and nonbridging oxygen atoms (NBO) in both the binary and ternary silicate glasses. The fraction of nonbridging oxygen was these spectra and found to increase with increasing praseodymium oxide content in the glass, The NBO contribution to the total O 1s spectrum for each glass sample has been simulated with contributions from the separate configurations SiOPr(III) and SiONa. The physical and thermal properties of these same glass samples indicate that Pr2O3 enters the glass network as an intermediate rather than a modifier oxide. The (chi) measurements indicate that chi(-1) follows a Curie-Weiss law behaviour and the negative Curie temperature (theta(p)) indicates an antiferromagnetic exchange interaction for all glass samples in this composition range.